Enhanced impact properties of functionally graded preplaced aggregate fibrous concrete slabs comprising alkali-activated slag and carbon nanotube grout

Abstract

Nowadays, cement manufacturing stands as the third most significant contributor to anthropogenic CO2 emissions. Alkali-activated techniques are emerging as a potentially more environmentally friendly alternate binder to mitigate the risks related to climate change. The current investigation utilizes the notion of preplaced aggregate concrete (PAC) and alkali-activated slag grouts comprising multi-walled carbon nanotubes (MWCNT) of 0.1 % dosage to implement functionally graded preplaced aggregate fibrous concrete slabs (FGPAFC). The optimum efflux time of alkali-activated slag grouts was determined through trials with various superplasticizer dosages and water-to-binder ratios. However, as it has not been investigated previously, the effect of alkali-activated grout made up of MWCNT on the impact strength of the FGPAFC slab deserves special focus. For this, seven different slabs were prepared, in which five three-layered FGPAFC slabs containing a steel fibre at a dosage of 3.5–4.5 % at a 0.25 % increment were provided at the upper and lower layers. At the same time, the middle layer contains 0–2 % fibres at 0.5 % increment. Using the same amount of fibre as in FGPAFC, a PAC slab with uniform fibre distribution is made to examine how effectively the three-layer arrangement performs. The slab underwent an impact test in accordance with the guidelines set forth by ACI Committee 544. The cracking and failure impact number, crack resistance at service and ultimate stages, impact ductility, the ratio of crack resistance, failure pattern, and its mechanism were examined. Findings reveal that the cracking and failure impact energies were enhanced by roughly 3–12 % and 15–53 %, respectively, by lowering the fibre content at the middle layer and raising it at the upper and lower layers of the FGPAFC slab from 3.0 progressively to 4.5 %. The contribution of steel fibre is more significant than MWCNT for enriching the impact resistance of FGPAFC. The findings derived from this study offer foundational data for subsequent comprehensive scientific examination of FPAFC subjected to impact.